When the Day Met the Night
by Nocturnal Introvert
Summary: Robbie never thought he'd care for a girl like Mabel Pines, and Mabel never thought Robbie was anything but a jerk. But when Wendy breaks up with Robbie unexpectedly, leaving boy-crazy Mabel to attempt to comfort him, their opinions of each other begin to change drastically. (Will eventually be RobbiexMabel)
1. Chapter 1: What Is Love?

It was a quiet, peaceful day in Gravity Falls, Oregon. Nothing seemed to be happening, as most of the inhabitants of the town were having a carefree, lazy day. It seemed like the entire town was at a standstill. Time seemed to pass a bit slower than usual, as if life was suddenly set to slow-motion mode. For Mabel Pines, it was a miserably boring day. Even fewer tourists than normal were visiting the gift shop of the Mystery Shack, where she had been forced to spend her morning cleaning. And even worse, everyone else seemed to be occupied: Stan was showing a group of people whatever scam he had found recently, Wendy and Soos were running the gift shop (to an extent, anyway), and Dipper was reading his book.

Without anyone to keep her company, Mabel felt like there was simply nothing fun to do today. She had flirted with all the guys who entered the gift shop (a total of two) for the majority of the morning with no luck. It became clear to her that she would have no luck fulfilling her dream of a summer romance here, so she finally decided to try another tactic. Mabel ran upstairs to her and Dipper's bedroom, put on her favorite sweater/headband combo, and returned to the gift shop.

"Hey Dipper, wanna go somewhere?" The young girl eagerly asked her twin brother. It was nearly noon, and she knew that their shift at the gift shop was almost over by now, so she was almost certain that Dipper would join her in relieving her boredom with a good, old-fashioned adventure. He was always up for that type of thing.

Sadly, Dipper didn't even bother to look up from his reading. And after what seemed like forever, he shook his head slowly.

"Nah, I'm busy. You go ahead Mabel." He replied with his head still buried in his book. "Maybe I'll catch up with you later."

Mabel pouted and started to walk away, when suddenly there was a hand on her shoulder. She turned around excitedly, hoping Dipper had changed his mind, only to find a tall ginger girl smiling down at her.

"You going to the town?" Wendy asked.

Mabel smiled and nodded quickly, thinking that maybe the teen would take some time off 'work' to hang out with her or something.

"I was supposed to meet Robbie there like, soon. You mind giving him this note if you see him?" The older girl asked, finding a scrap of paper somewhere behind the counter and scrawling something onto it quickly.

Mabel tried to hide her disappointment, keeping a smile plastered across her face. "Sure!" She said with a nod, taking the note once Wendy had finished writing. She shot a quick glance at her brother, who she now noticed was staring at Wendy. He didn't seem too happy that Wendy was sending what was probably a love note to her boyfriend. Mabel held up the piece of paper, stuck her tongue out at her brother, and continued on her way to the Shack's exit.

* * *

Once she was in the town, Mabel instantly ran over to the first boy she saw. He was standing in front of the grocery store, and he appeared to be around her age. He was a perfect target.

"Hiya! I'm Mabel! Are you a parking ticket? Because you've got FINE written all over you!" Mabel giggled, trying her best to look adorable.

"W-what?" The boy stuttered, completely shocked, turning around to look at her. After seeing that Mabel was only about two inches away from his face, he backed away from her quickly and ran inside the store.

"Rats! I must have scared him away with my girlish charm! I better tone it down a bit..." The young girl told herself. Just as Mabel turned around, she was suddenly face-to-face, or more like face-to-chest, with a tall teenage guy in a black hoodie. From the almost overpowering smell of anger, hormones and body spray radiating from the teen, Mabel instantly knew who it was.

"Hey loser, where's that wimpy brother of yours?" Robbie snickered, glaring down at Mabel menacingly.

Mabel backed up a bit and glared right back up at the older boy, rolling her eyes. Mabel didn't hate anyone. She was a firm believer in second chances, and she was sure Robbie had an excuse for being such a jerk to her brother, but right now, he had no excuse to be rude to her. At the moment, he was aggravating the usually happy-go-lucky girl.

"He's at the Mystery Shack, with _your_ girlfriend!" Mabel replied with a smirk. "Oh! And Wendy gave me a note for you!" She added, reaching into her sweater pocket and getting out the piece of paper.

Robbie looked skeptical, but snatched the note from her hands nonetheless. He silently mouthed the words as he read the note.

Mabel read Robbie's lips and couldn't hold back a slight giggle once he had finished.

"She's breaking up with you…in a note?" She laughed. But once she saw the look on Robbie's face, a mixture of anger and hurt, her smile disappeared. She cleared her throat. "I mean, that's so terrible! Sorry, Robbie!" Mabel whispered, awkwardly patting the older boy's shoulder.

Robbie took a step away from her and scowled. He crumpled up the note and threw it onto the ground. "Ugh! This is totally lame!" He complained, pulling his hood over his head and shoving his hands into his hoodie pocket. He turned to sulk away, but Mabel grabbed his arm.

"Robbie…I'm super sorry. Wendy shouldn't have broken up with you like that. That was totally uncalled for. Any girl would be lucky to date you, even if you are kind of a jerk." Mabel said. She looked up at the teen and smiled somewhat sympathetically. She wasn't exactly sure why she was comforting Robbie after how he treated her brother, but she really hated seeing people sad.

Robbie looked down at her, his face unreadable. "Yeah, whatever, you're right. Now get off." He grumbled, prying her hand off his arm with little effort and turning around again.

Suddenly, Mabel had an idea.

"Robbie! Wait!" She called, stepping toward him.

He didn't turn around, but he stood still for a moment.

Mabel played with her hair, suddenly feeling slightly nervous. "When I said any girl…um, well, I'm always an option?" She offered.

Robbie turned around to face the younger girl and looked down at her questioningly. "What?" He half-laughed. "Are you kidding? Aren't you like…ten or something?"

Mabel crossed her arms. "Twelve." She corrected. "At least give me a chance! People tell me I'm _irresistible_!" She winked and smiled up at the teen, her braces shining in the sunlight.

Robbie blinked at her for a while, unsure of how to respond. Honestly, he was hoping that she was just messing around. When she said nothing, he let out a sigh.

"Look, do you even realize how bad it'd look if I dated a dorky pre-teen? I have an image to uphold, kid!" Robbie scoffed, seemingly shocked by the mere idea of it.

Mabel shrugged. "Who cares what people think?" She asked, swinging her arms dramatically to emphasize her point.

Robbie looked at her from head to toe, making a disgusted face.

"Obviously not you…" He muttered, pointing at her sweater. Before he could attempt to get away again, Mabel grabbed his arm tightly and looked up at him, pouting and making puppy-dog eyes. Robbie looked down, wide eyed with shock, obviously beginning to get irritated.

"Pretty please?" Mabel begged, fluttering her eyelashes.

Robbie groaned. "Alright, fine! Whatever! As long as you promise you'll leave me alone after this!" He muttered.

Mabel grinned victoriously and jumped up and down for a bit. "I promise!" She said, twirling around. "I'm dating an older man!" She added with a dream-like sigh.

"Yeah, yeah, keep it down. There are people around." Robbie growled. "Come on; let's just get this over with." As he spoke, he turned around yet again and began to walk down the street. This time, much to his surprise, Mabel didn't try to stop him. She skipped along after him, still not sensing his irritation.

They kept walking until they got to the park near Smoky Toe's All You Can Eat Restaurant. Robbie stopped for a second and looked over his shoulder to see if Mabel was having trouble keeping up with him. Much to his dismay, she was right behind him. With a sigh, he quickened his pace and walked into the park.

"Ooh! A park! What a great place for a date!" Mabel exclaimed, looking pleased.

Robbie sighed. "Whatever. I'm just here to do some graffiti. Then I'm leaving, and our little 'date' is over, okay?" He grumbled.

Mabel pouted. "Aw! But Robbie! Think of all the fun we could have!" She complained.

Robbie scowled. "Fun?" He laughed. "Apparently we have different ideas on what 'fun' is, Mabel." The teen shook his head and removed the backpack he'd been carrying. He took out two cans of spray paint then scoped the area for a good place to do some graffiti, deciding to ignore the younger girl for a bit.

"You're going to do graffiti in a park…in the middle of the day? Isn't that illegal? What if someone sees you?" Mabel asked, sounding a bit confused. She walked over to the makeshift swing set and sat down, watching Robbie from a distance.

"Pfft-Right, like someone would see me when we're in an empty park." Robbie said, rolling his eyes.

Mabel shrugged. "Well, you never know, someone could always walk past." She told him.

Robbie sighed. "Okay, well if you're so concerned, how 'bout you tell me if you see anyone around here?" He asked, sounding a bit aggravated.

"Okay!" The younger girl exclaimed, beginning to swing a bit higher so she could tell if anyone was nearby. "The coast is clear for now!" She told him, staring out toward the sidewalk intently.

Robbie nodded, his eyebrows raised a bit, as if it was the most obvious thing in the world. "Good to know." He muttered, dragging his backpack over toward the clock tower and starting to work on his latest 'masterpiece'.

After he had painted for a while, he looked over at Mabel. She was still looking outside the park to make sure he didn't get caught. Robbie shook his head and looked back toward his painting. It hadn't taken him very long, but he was quite pleased with how it was turning out so far. He had gotten the idea as soon as he read Wendy's note to him, because it was exactly how he had felt. And now, as he continued to work on it, he felt like he was painting his very thoughts onto the clock tower. Thoughts that no one would ever imagine him having. It was like he was showing the whole town just who he was underneath his 'tough guy' exterior. He usually didn't paint things like this, he kept them to himself in his sketchbook, but once the inspiration had hit him, he knew that he should paint this, and not another 'explosion' or skull or something like that.

Having Mabel with him made it a bit hard to paint something so serious to him, but he kept at it. He had never really had a problem with Mabel. It was Dipper who he didn't like. Dipper, who waltzed in and acted like he was worthy of hanging around Wendy. Wendy, who Robbie had been in love with since he moved to the town. It wasn't like he could blame Dipper for liking her, but it annoyed him that Dipper thought he should be the one to be with Wendy. But now it was Mabel who annoyed him. Mabel with her stupid sweaters and equally stupid headbands, acting like she could cheer him up when she obviously had no clue how he was feeling. Trying to flirt with him as if it would somehow help. Robbie scowled and added some details to his painting.

Mabel continued to swing and keep lookout, but before too long she had grown bored of doing nothing but stare at an empty sidewalk. Her curiosity was beginning to get the best of her, so decided to look over at whatever Robbie was painting.

"Oh wow! That's super good!" Mabel exclaimed, putting her hands on her cheeks and nearly falling out of the rickety swing. She slowed down a bit, jumped out of the swing, and ran over toward Robbie, admiring his painting with genuine surprise. She glanced from the 'muffin-explosion' on the water tower to his most recent work, her eyebrows raised in shock. "Have you been taking art lessons?" She asked him.

Robbie glanced over his shoulder at her and shrugged. "Nah, I've just been more inspired lately." He said plainly, putting the finishing touches on his painting. Robbie stood up and took a few steps back to admire his work.

He had painted the shadow of a man whose posture was like a crumpled piece of paper. There was a heart-shaped hole in his chest, and rain was pouring down on him. It had turned out exactly as he wanted it to.

As Mabel got a closer look at the painting, she pouted. "Wow! This is so depressing! Why doesn't the poor guy have a heart?" She asked.

Robbie rolled his eyes and put the paint cans back into his backpack. He was a bit angry that Mabel was basically insulting his painting. His painting that she would never understand, just like his feelings for Wendy that she would never understand. "Because a stupid girl ripped it out." The older boy muttered, half to himself. "Love sucks, Mabel. Remember that." He added, a bit louder.

Mabel gasped. "Love does not suck, mister! Love is amazing and powerful and super beautiful!" She told him, putting her hands on her hips.

Robbie laughed quietly. "What makes you say that? You're twelve, and I'm pretty sure you've never even been in love before." He told her, a bit harshly. "If you think love is so great, then you've obviously never had your heart broken before."

Mabel was silent for a moment. She thought back to the note Wendy had wrote to Robbie earlier and his reaction to it. Suddenly, she realized that Robbie must actually really care about Wendy. Maybe that's why he was always so mean to Dipper. And maybe he was right; she really did know nothing about what it was like to be in love.

"It's a really good painting…" Mabel whispered, attempting to smile, before turning and running toward the exit of the park.

Robbie turned around and watched her leave, and he felt slightly bad about what he'd said to Mabel. Even if he was upset, and even if he was actually sort of relieved that she'd left, he still felt like a jerk. Usually, he wouldn't care. But something about the girl's kind, braces-filled smile made him regret being so mean to her. He wasn't sure why, but for some reason, he found himself actually caring that he'd made her upset.

"Great…" Robbie muttered, slinging his backpack over his shoulder and taking off after her.


	2. Chapter 2: Our Little Secret

"Kid, wait up." Robbie called. "I didn't mean to flip out at you like that."

He had caught up with Mabel quite quickly, despite his efforts not to. He wanted to go home and pretend none of this ever happened, but it was as if some supernatural being was pushing him along in her direction.

As soon as Robbie caught up to her, part of him wanted to turn around and just leave already. Part of him thought he'd dealt with Mabel enough for one day. But something in the back of his mind told him to at least talk to the younger girl, even if she had been irritating him more than anything just a moment ago. Sure, he knew he was probably right; Mabel knew absolutely nothing about love, nor did she know anything about how Robbie was feeling. And he certainly knew that she was only making things worse by flirting with him in attempt to somehow comfort him. But for whatever reason, Robbie just couldn't stay mad at her, no matter how hard he tried. He knew that she hadn't been trying to make things worse. And after seeing how hurt she looked after he'd snapped at her made Robbie think that maybe he'd been a bit too harsh. He hadn't meant to upset her; he just didn't really want to be around her at that exact moment.

He was hurt and confused, so he took it out on her. That was something he unintentionally did to people an awful lot. Usually Robbie hid his true emotions somewhere deep inside in attempt to distance himself from other people. He knew he was a jerk sometimes, but that was just his way of keeping himself from getting hurt. But for some reason, when he was around Mabel, he had begun to let his guard down. He actually started to let himself care about Mabel. Normally, he wouldn't have cared any less about making her upset. But this time it was different. He'd rarely seen Mabel without a smile on her face. And, for a reason he didn't quite understand, the fact that he had upset her really bothered him.

"Huh?" At the sound of Robbie's voice Mabel skidded to a stop and turned around. When she realized that Robbie had followed her she let out a quiet gasp of surprise. Even though Mabel was generally an incredibly optimistic person, she hadn't expected Robbie to care that she'd left, let alone seemingly notice that she had been upset by what he said. Mabel could tell she hadn't been wanted just moments ago, and right now she was quite curious as to what had made Robbie suddenly change his mind.

She started to get the feeling that maybe he wasn't quite what she'd thought him to be. Maybe Robbie actually did care. Maybe he did have a heart under all that 'coolness' and body spray.

"Look, I-I guess what I'm trying to say is..." Robbie trailed off and sighed. "I'm sorry. So like, don't worry about what I said. I seriously didn't mean it or anything. I'm...I'm just kinda angry, I guess." He told her, shrugging and avoiding her questioning gaze. Robbie wasn't exactly used to apologizing to anyone, especially not to people like Mabel. Usually doing something like this would have been completely out of the question. But right now he felt like he should apologize to her, even if it rather humiliated him to do so.

Mabel was really surprised that Robbie actually bothered to apologize, but she tried her best to just shrug it off, hoping to not offend him any more than she already had. "Oh, don't worry about it." She said, giving him a wide grin and hoping to lighten the surprisingly serious tone of the conversation.

Even though what he'd said really had hurt her, she didn't want him to know that. She didn't like to be seen as a person who was easily upset. Not because she wasn't, but because she didn't like it when people worried about her. Dipper was constantly fussing over her whenever she got upset. And she didn't like to cause other people to worry. She liked it when everyone was happy, even if she wasn't. So she did her best to act as happy as possible all the time, because she thought it'd help others feel happy too. Generally she was a very optimistic and joyful person on her own, but sometimes she let the negative thoughts in the back of her mind get to her, and the unhappiness she felt in those moments was astonishing. But after hearing Robbie apologize to her, which she figured was a rare event to witness, she felt much better than she had. She still felt bad for misunderstanding how he felt about Wendy, but it was merely an afterthought at the moment.

"You were right, anyway." Mabel told him, never allowing the bright smile to leave her face. "I don't know anything about love…" She made it seem like it was just a lighthearted statement, but in reality there was more to it than just that. She really did know that Robbie was right.

All Mabel wanted was the kind of love that she saw in her supernatural romance novels. She wanted a love that could overcome anything; a love that would last forever. She wanted someone in her life that she could make happy, someone who could make her actually feel as happy as she usually seemed. She wanted someone who would accept her, even if she was different and a little bit weird. And for some reason she felt incredibly hopeful about finding that person now that she was in Gravity Falls. At home she'd been considered a freak. Mabel was a girl with an always present smile who knitted in her spare time, almost strictly wore sweaters, and was unhealthily obsessed with glitter, vampires, and pigs. Back in Piedmont, she just wasn't 'normal' by the standards of most people her age. But in this town she felt like she was normal. Especially when compared to everything else. And she felt like if she met someone here who was even less normal than her, then maybe they'd accept her and love her the way she was. She knew it was silly, but these thoughts were still there in the back of her mind. Plus, her overwhelming kindness did tend to make her fall in love quite quickly. She saw the good in everyone. Mabel did tend to rush into relationships. She knew that. But it hadn't been brought to her attention that what she was feeling wasn't true love until Robbie had pointed it out. What she was feeling was nothing more than loneliness and desperation usually mixed in with a bit of admiration.

"I mean, really, my kind of 'love' generally only lasts a week. Then the boy leaves, moves on, or turns out to be a zombie or whatever." She said, shrugging and giggling a bit at herself.

But behind her seemingly carefree smile, there was a hint of some other emotion that glimmered in her deep brown eyes for a split second. If Robbie hadn't glanced up at her exactly when he did, he wouldn't have noticed it; and he wanted to pretend he didn't see it at all. But he knew that he wasn't just imagining things. Mabel was hurting. She really was upset. And it struck him somewhere deep inside. He had somehow managed to see the sadness and loneliness that so few people ever saw in usually cheerful Mabel. Robbie saw what she wanted no one to know about her. That underneath the perpetual joy she always seemed to emanate, she actually did get genuinely upset sometimes. Robbie wished he hadn't seen it. Because it was what kept him from just nodding and leaving at that exact moment; it changed his entire opinion about her. Now Mabel didn't seem so annoying all of a sudden. Something about the emotion in the younger girl's eyes kept his feet planted on the ground right where he was in front of her. He just couldn't leave after seeing her like that. Maybe it was because he knew exactly how she was feeling.

Robbie really had loved Wendy. He didn't believe in love at first sight, but he couldn't deny that he knew he loved Wendy almost exactly upon meeting her. Something about Wendy Corduroy made Robbie completely insane. Whenever he was around her he felt a strange fluttering feeling in his gut. Words escaped him. His palms sweated mercilessly. And somehow, he loved every moment of it. If that wasn't love, he didn't know what was. But right now, just thinking of Wendy pained him. Wendy had made him so happy. And without her in his life, though it had only been a few hours since they'd broken up, he felt like all the happiness he'd ever had was being sucked right out of him. When they'd first started dating he was completely overjoyed. But now that it was over, he felt like maybe everything he thought they'd had was never even real in the first place. He never knew he could go from being on top of the world to being at the bottom of the universe so quickly. He was suddenly back to square one; keeping his distance from everyone and hiding his feeling away somewhere inside himself to keep from getting hurt. But when he saw all the loneliness and sadness in Mabel's eyes he felt like he could identify with exactly how she felt at the moment. They were both different. They were both lonely. And they both wore their personalities like masks to hide their true emotions. He never thought he would have a connection like that with someone like Mabel Pines.

Robbie sighed and ran a hand through his hair. He wasn't used to expressing his emotions. Usually he loathed the thought of telling another person what was on his mind. But today was just full of surprises. "Look, kid. Just-Forget about what I said, okay? There's nothing wrong with having crushes while you're young. Because hey, I'm still young too; and who's to say what we're feeling isn't really love? 'Cause there's always a reason you like someone, you know? So maybe it's not 'love love' or whatever, but I bet you do know what it's like to love someone." He told her. "I mean, you're like, super nice all the time. Even today, you tried to help me out even though I'm a major jerk to your brother. You care about people a lot. Way too much in my opinion. And in a way, caring about someone is loving them, right?" When Mabel didn't say anything in response, he took it as his cue to keep talking. "Point being, I'm really sorry I snapped at you when you were just trying to help me out. Thanks for trying to get my mind off things."

After he finished rambling, he jammed his hands in his pockets and finally looked up at Mabel. She was staring at him with her eyes wide and her head tilted slightly in complete and utter confusion. Robbie felt his cheeks heat up. He instantly regretted what he'd said. He knew he must have messed something up or said something in a really stupid way. He knew he probably completely destroyed his image. Not like he cared what this girl thought anyway, but still. Just as he was about to abandon ship and finally get himself away from the less irritating of the Pines Twins, Mabel opened her mouth.

"Oh wow." She said quietly, seemingly in shock. "I don't know what I expected...but it was soo not that. What even was that, Robbie? Where did that even come from? Oh wow. Wow, wow, wow."

Robbie shook his head and rolled his eyes. "Oh shut it, kid. That...I...I didn't..." He trailed off, huffed, and yet again turned to walk away.

"Hey, wait! Why do you always try to walk off whenever I want to talk to you?" Mabel asked him.

Robbie glanced at her over his shoulder and saw a playful glimmer suddenly replacing the sadness that had been present in her eyes just moments ago.

"Robbie, that was the sweetest thing I've ever heard! Well, outside of Wolfman Bare Chest anyway. That seriously just made my day!" Mabel exclaimed. "Who knew you were such a softie?" She teased, grinning widely.

Robbie scoffed, trying his best not to show how embarrassed he was. "I am _not_ a softie. I-I was just…Look, squirt, if you tell anyone- and I mean _anyone-_ about this you will regret it. Don't tell your brother, your friends or even your pig. Just…Forget that even happened. I don't…I'm not usually like this, I swear!"

Mabel giggled and nodded. "Oh, of course not, Robbie. Don't worry, I won't tell anyone. It can be our little secret."

* * *

**A/N: I finally decided to update this story! Yay! I was really hesitant to upload this because it's kinda personal to me, it's not my best work, and it's definitely a bit OOC. But, depending on some things, I might end up writing a few more chapters for this. Or fixing it up a little bit. Who knows? Anyway, thank you to everyone who's supported this story despite the fact that I took over a month to update! **


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